The Denver District Attorney’s office on Wednesday charged a man with murder and assault stemming from the Jan. 1 deadly shooting of another man in a southwest Denver home.

Robert Rubio, 26, remains in the Downtown Denver Detention Center on charges of second-degree murder and assault in the death of Troy Anthony Martinez, 21, the city’s first homicide of 2013.

Police say Rubio was living in the home in the 1000 block of South Alcott Street, where Martinez had been visiting with another man, 22, who was also struck by gunfire.

Rubio’s relatives have said they believe he fired in defense of his younger brother, Jason, who was also staying at the home. Court documents offer few glimpses into a motive but note that an unidentified witness pegged the older Rubio as the gunman. A police report also notes the involvement of the Denver police gang bureau but does not elaborate.

Rubio was convicted in 2005 and 2006 for misdemeanor charges of possession of drug paraphernalia. In 2008, he was charged with first-degree assault but pleaded guilty to a lesser charge of drugging a victim, according to Colorado Bureau of Investigation records. Also, Denver police arrested him July 31, 2009, on a felony assault charge, records show.

Martinez was killed the day after he turned 21. He too had a criminal record. In 2011, he was charged with aggravated robbery and convicted of a reduced charge of drugging a victim. He was placed on probation for five years.

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